Jeffers Gregory T, Bruce James L, McDonough Patrick L, Scarlett Janet, Boor Kathryn J, Wiedmann Martin
Department of Food Science, 412 Stocking Hall, Cornell University, Ithaca, NY 14853, USA1.
Qualicon Inc., Wilmington, DE 19880, USA2.
Microbiology (Reading). 2001 May;147(Pt 5):1095-1104. doi: 10.1099/00221287-147-5-1095.
Listeria monocytogenes isolates from human sporadic and epidemic cases (n=119) and from animal cases (n=76) were characterized by automated ribotyping and PCR-restriction fragment length polymorphism (PCR-RFLP) typing of the virulence genes actA and hly. This combination of typing methods differentiated 39 distinctive strains, each reflecting a unique combination of ribotypes, hly and actA alleles. Simpson's index of discrimination indicated a high discriminatory ability of ribotyping for both animal (0.867) and human isolates (0.857), which was further increased by the addition of hly and actA typing (0.916 and 0.904, respectively). Ribotype and hly allele data were further used to group isolates into three genetically distinct lineages. Each lineage is composed of several ribotype fragment subsets, each of which contains multiple ribotypes characterized by common ribotype fragments. To determine whether certain clones of L. monocytogenes show indications for unique pathogenic potential or host specificity, frequency distributions for five genetic characteristics (i.e. lineage, ribotype, ribotype fragment subset and hly and actA allele) were calculated for isolates from animal cases, human epidemic cases and human sporadic cases. Lineage III isolates were found less frequently in human cases (1 of 119 isolates) than in animal cases (8 of 76 isolates; P=0.003). These results suggest the possibility of host specificity for non-primate mammals among lineage III strains. In addition, lineage I strains were found more frequently among human cases than among animal cases (P<0.001). Among the eight hly alleles observed, hly allele 1 was more common among human isolates as compared to animal isolates (P=0.002). We also identified one ribotype (DUP-1030) which was significantly more common among animal isolates (P=0.005) and one ribotype (DUP-1038; lineage I) which was significantly more common among human epidemic isolates as compared to human sporadic isolates (P<0.001). These findings confirm the presence of clonal groups of L. monocytogenes, which appear to be characterized by unique virulence or host specificity patterns. This study also establishes baseline data describing the genetic diversity of human and animal L. monocytogenes isolates which can be utilized in future surveillance programmes to track the emergence of new strains.
采用自动核糖体分型法以及对毒力基因actA和hly进行聚合酶链反应-限制性片段长度多态性（PCR-RFLP）分型，对从人类散发病例和流行病例（n = 119）以及动物病例（n = 76）中分离出的单核细胞增生李斯特菌进行了特征分析。这种分型方法组合区分出了39种不同的菌株，每种菌株都反映了核糖体分型、hly和actA等位基因的独特组合。辛普森鉴别指数表明，核糖体分型对动物分离株（0.867）和人类分离株（0.857）均具有较高的鉴别能力，通过增加hly和actA分型，鉴别能力进一步提高（分别为0.916和0.904）。核糖体分型和hly等位基因数据进一步用于将分离株分为三个遗传上不同的谱系。每个谱系由几个核糖体分型片段子集组成，每个子集包含以共同核糖体分型片段为特征的多个核糖体分型。为了确定单核细胞增生李斯特菌的某些克隆是否显示出独特的致病潜力或宿主特异性迹象，计算了动物病例、人类流行病例和人类散发病例分离株的五个遗传特征（即谱系、核糖体分型、核糖体分型片段子集以及hly和actA等位基因）的频率分布。发现谱系III分离株在人类病例中出现的频率（119株分离株中的1株）低于动物病例（76株分离株中的8株；P = 0.003）。这些结果表明，谱系III菌株对非灵长类哺乳动物可能具有宿主特异性。此外，发现谱系I菌株在人类病例中出现的频率高于动物病例（P < 0.001）。在所观察到的8个hly等位基因中，hly等位基因1在人类分离株中比在动物分离株中更常见（P = 0.002）。我们还鉴定出一种核糖体分型（DUP-1030）在动物分离株中显著更常见（P = 0.005），以及一种核糖体分型（DUP-1038；谱系I）在人类流行分离株中比在人类散发分离株中显著更常见（P < 0.001）。这些发现证实了单核细胞增生李斯特菌克隆群的存在，这些克隆群似乎具有独特的毒力或宿主特异性模式。本研究还建立了描述人类和动物单核细胞增生李斯特菌分离株遗传多样性的基线数据，可用于未来的监测计划以追踪新菌株的出现。
